Calcium phosphate cement promotes the stability of osteoporotic lumbar pedicle screw by enhancer-injecters with different number of holes.

BACKGROUNDS: This study aimed to compare whether Calcium phosphate cement (CPC) promotes the stability of osteoporotic lumbar pedicle screw by enhancer-injecters with different number of holes. METHODS: Through a self-designed bone cement injection device, the pedicle screw canal was strengthened with calcium phosphate bone cement, and divided into 4-hole group, 6-hole group, 8-hole group, straight pore group and the control group. The screw was inserted into the mechanical test module, the Maximum insertion torque and Maximum axial pull-out strength were recorded, and the distribution of calcium phosphate bone cement was analyzed by CT and X-ray. The data results were analyzed using SPSS19.0 statistical software package. RESULTS: The distribution of bone cement in different reinforcement groups was different and showed regularity. The bone cement in the 4-hole group was roughly located in the head 1/3 of the screw, the 6-hole group was located in the middle 1/3 of the screw, and the 8-hole group was located in the caudal 1/3 of the screw. Compared with the control group, the maximum axial pull-out force of screws in the lateral hole and full screw tunnel reinforcement group was significantly increased. There was no significant difference between the 4-hole, 6-hole and straight pore groups. There was no difference in the screw-in torque between the reinforcement groups, and they all increased significantly compared with the control group, and the difference was statistically significant. After the screw was pulled out, the interface between the bone cement and the polyurethane material was fractured, and a tight package was formed with the screw. CONCLUSIONS: Enhancer syringes with different hole numbers combined with CPC bone cement injection can significantly increase the maximum screw pull-out force. The 8-hole group has a smaller pull-out force and is relatively prone to leakage of reinforcing material, which lacks safety in use. The local reinforcement of 4-hole and 6-hole sheath can play a similar role to that of total nail tunnel reinforcement.

A novel bone cement injector augments Chinese osteoporotic lumbar pedicle screw channel: a biomechanical investigation.

BACKGROUND: The study aimed to (1) create a series of pedicle injectors with different number of holes on the sheath especially for the Chinese elderly patients and (2) further investigate the effects of the injectors on the augmentation of pedicle screw among osteoporotic lumbar pedicle channel. METHODS: This study used the biomechanical test module of polyurethane (Pacific Research Laboratory Corp, USA) to simulate the mechanical properties of human osteoporotic cancellous bone. The bone cement injectors were invented based on anatomical parameters of lumbar pedicle in Chinese elderly patients. Mechanical test experiments were performed on the bone cement injectors according to the three groups, namely, a local augmentation group, a full-length augmentation group, and a control group. The local augmentation group included three subgroups including 4-hole group, 6-hole group, and 8-hole group. All holes were laterally placed. The full-length augmentation group was a straight-hole injector. The control group was defined that pedicle screws were inserted without any cement augmentation. Six screws were inserted in each group and the maximum insertion torque was recorded. After 24 h of injecting acrylic bone cement, routine X-ray and CT examinations were performed to evaluate the distribution of bone cement. The axial pull-out force of screws was tested with the help of the material testing system 858 (MTS-858) mechanical tester. RESULTS: The bone cement injectors were consisted of the sheaths and the steel rods and the sheaths had different number of lateral holes. The control group had the lowest maximum insertion torque as compared with the 4-hole, 6-hole, 8-hole, and straight pore groups (P < 0.01), but the differences between the 4-hole, 6-hole, 8-hole, and straight pore groups were no statistical significance. The control group had the lowest maximum axial pull-out force as compared with the other four groups (P < 0.01). Subgroup analysis showed the 8-hole group (161.35 ± 27.17 N) had the lower maximum axial pull-out force as compared with the 4-hole group (217.29 ± 49.68 N), 6-hole group (228.39 ± 57.83 N), and straight pore group (237.55 ± 35.96 N) (P < 0.01). Bone cement was mainly distributed in 1/3 of the distal end of the screw among the 4-hole group, in the middle 1/3 and distal end of the screw among the 6-hole group, in the proximal 1/3 of the screw among the 8-hole group, and along the long axis of the whole screw body in the straight pore group. It might indicate that the 8-hole and straight-hole groups were more vulnerable to spinal canal cement leakage. After pullout, bone cement was also closely connected with the screw without any looseness or fragmentation. CONCLUSIONS: The bone cement injectors with different number of holes can be used to augment the pedicle screw channel. The pedicle screw augmented by the 4-hole or 6-hole sheath may have similar effects to the straight pore injector. However, the 8-hole injector may result in relatively lower pull-out strength and the straight pore injector has the risks of cement leakage as well as cement solidarization near the screw head.

Fabrication and Characterization of MSQ Aerogel Coating on ePTFE Thin Films for Cable Sheaths.

With methylsilsesquioxane (MSQ) aerogels synthesized by the sol-gel method as a raw material and Si-Ti sol as a binder, an alcohol-based aerogel slurry consisting of only MSQ aerogel and Si-Ti sol was prepared and coated on expanded polytetrafluoroethylene (ePTFE) to form an MSQ aerogel coating layer, followed by low-temperature heat treatment. The effect of Si-Ti sol content on the microstructure of the MSQ aerogel coating layer was investigated, and the properties of a typical MSQ aerogel-layer-coated ePTFE film were evaluated. The results show that Si-Ti sol has an important role in terms of film-forming capability, surface smoothness, flexibility, and powder dropping of the MSQ aerogel coating layer. With a Si-Ti sol of 10.5 wt.% content as a binder and after heat treatment at 170 °C for 30 min, the coated ePTFE flexible thin film with a layer thickness of 30 µm shows high uniformity, integrity, and electrical insulation properties, with an elongation at break decrease over 130%, a thermal conductivity of 0.1753 W/(m·K) at 25 °C, a dielectric constant of 16.5674, and a dielectric loss of 0.06369, which can be promisingly applied in cable sheaths.

Reduction of Leg Pain by Oxiplex Gel After Lumbar Discectomy in Patients With Predominant Leg Pain and Elevated Levels of Lower Back Pain: A Prospective, Randomized, Blinded, Multicenter Clinical Study.

STUDY DESIGN: A prospective, randomized, blinded, multicenter clinical study. OBJECTIVE: To evaluate carboxymethylcellulose/polyethylene oxide gel (Oxiplex) in improving clinical outcomes in subjects having predominant leg pain and elevated low back pain undergoing first-time lumbar discectomy for disk herniation. SUMMARY OF BACKGROUND DATA: Clinical studies in the United States and Italy found that Oxiplex reduced leg pain after decompression surgery. METHODS: A total of 68 subjects with herniated lumbar disk were enrolled and randomized into treatment (surgery plus gel) or surgery-only control groups. A prospective statistical analysis assessed the effect of gel in the severe back pain subgroup (prespecified as greater than or equal to median baseline back pain of the population studied). All subjects except 2 controls lost to follow-up completed the study. Preoperative and postoperative visual analogue scale leg pain scores were analyzed and compared between groups at 60 days after surgery. RESULTS: There were no serious adverse events or neurological safety concerns reported in any patients. Gel-treated patients had statistically significantly lower visual analogue scale leg pain scores at study end compared with controls (P=0.0240), representing a 21% additional reduction in leg pain compared with surgery alone in the severe baseline back pain subgroup (P=0.0240). The proportion of subgroup patients experiencing zero leg pain at study end was significantly higher in the gel treatment group (60%) than in the control group (23%) (P=0.0411). CONCLUSIONS: The data from this study confirm and extend results of 2 previous studies in Italy and the United States that reported statistically significantly greater reductions in leg pain in gel-treated patients with severe preoperative low back pain compared with patients who only underwent decompression surgery.

Comparison of 2 kinds of pedicle screws in primary spinal instrumentation: biomechanical and interfacial evaluations in sheep vertebrae in vitro.

STUDY DESIGN: Expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) were inserted in sheep vertebrae in vitro and were evaluated by performing biomechanical tests, radiographic examinations and histological observations. OBJECTIVE: The objective of the study was to compare the biomechanical and interfacial performances of EPS and PMMA-PS in sheep lumbar vertebrae in vitro. SUMMARY OF BACKGROUND DATA: It is a great challenge for orthopedic surgeons performing transpedicular fixation in the osteoporotic spine. It was reported that either the EPS or PMMA-PS could increase the screw stability. However, there are no studies comparing the 2 kinds of screws especially in primary spinal instrumentation. METHODS: A total of 60 sheep lumbar vertebrae were randomly divided into 3 groups. A pilot hole was made in advance in all samples using the same method. Thereafter, the conventional pedicle screw (CPS) was inserted directly into the pilot hole in the CPS group; the hole in PMMA-PS group was first filled with polymethylmethacrylate (PMMA; 1.0 mL) and then inserted with CPS; and the EPS was inserted directly into the vertebrae in EPS group. After a period of 24 hours, biomechanical tests were performed to evaluate screw stability, and x-ray examination, micro-computerized tomography analysis, and histologic observation were performed to evaluate the interface between screw and bone. RESULTS: Compared with the stability of CPS, those of EPS and PMMA-PS were significantly enhanced. However, no significant differences were detected between the stabilities of EPS and PMMA-PS. The PMMA surrounding the screw blocked direct contact between bone and screw and formed a "screw-PMMA-bone" interface in the PMMA-PS group. There was a "screw-bone" interface in both CPS and EPS groups. Nevertheless, the expanded anterior part of EPS formed a claw-like structure pressing the surrounding bone trabeculae, which made the local bone tissue more compacted and denser than that in the CPS group. CONCLUSIONS: EPS can enhance the screw stability as markedly as the traditional PMMA-PS in primary surgery, and EPS can form a better immediate interface between screw and bone compared with PMMA-PS. EPS also can effectively avoid thermal injury, leakage, and compression caused by PMMA. A great feasibility was proved in this study to perform comparisons between the 2 kinds of pedicle screws in osteoporotic sheep vertebrae in vivo in the further research. In conclusion, we propose that EPS has a great application potential in augmentation of screw stability in the clinic.

In vivo study of a novel 3D-printed motion-preservation artificial cervical corpectomy construct: short-term imaging and biocompatibility evaluations in a goat model.

BACKGROUND: Nonfusion technologies, such as motion-preservation devices, have begun a new era of treatment options in spine surgery. Motion-preservation approaches mainly include total disc replacement for anterior cervical discectomy and fusion. However, for multisegment fusion, such as anterior cervical corpectomy and fusion, the options are more limited. Therefore, we designed a novel 3D-printed motion-preservation artificial cervical corpectomy construct (ACCC) for multisegment fusion. The aim of this study was to explore the feasibility of ACCC in a goat model. METHODS: Goats were treated with anterior C3 corpectomy and ACCC implantation and randomly divided into two groups evaluated at 3 or 6 months. Radiography, 3D CT reconstruction and MRI evaluations were performed. Biocompatibility was evaluated using micro-CT and histology. RESULTS: Postoperatively, all goats were in good condition, with free neck movement. Implant positioning was optimal. The relationship between facet joints was stable. The range of motion of the C2-C4 segments during flexion-extension at 3 and 6 months postoperatively was 7.8° and 7.3°, respectively. The implants were wrapped by new bone tissue, which had grown into the porous structure. Cartilage tissue, ossification centres, new blood vessels, and bone mineralization were observed at the porous metal vertebrae-bone interface and in the metal pores. CONCLUSIONS: The ACCC provided stabilization while preserving the motion of the functional spinal unit and promoting bone regeneration and vascularization. In this study, the ACCC was used for anterior cervical corpectomy and fusion (ACCF) in a goat model. We hope that this study will propel further research of motion-preservation devices.

In vivo study of pedicle screw augmentation using bioactive glass in osteoporosis sheep.

STUDY DESIGN: Augmentation of pedicle screws with bioactive glass (BG) was performed in osteoporotic ovine spine in vivo. Biomechanical tests, micro-computed tomography (CT) analysis, and histologic observation were performed. OBJECTIVE: To investigate the biomechanical stability of pedicle screws augmented by BG in osteoporotic sheep and observe the bone-screw interface histologically. SUMMARY OF BACKGROUND DATA: There is little information on the long-term biomechanical performance and screw-bone interfacial bonding of pedicle screws augmented with BG in osteoporotic spine in vivo. METHODS: Twelve months after ovariectomy combined with methylprednisolone injection, 8 adult female sheep were randomly divided into 2 groups (3- and 6-mo time point groups). In each time point group, pedicles were randomly selected from the lumbar spine (L1-L6) and implanted with (1) pedicle screw alone; (2) pedicle screw augmented by polymethylmethacrylate; or (3) pedicle screw augmented by BG. Three and 6 months after implantation, animals were labeled with tetracycline and calcein before being killed. Then vertebrae with pedicle screws were obtained, and a micro-CT scan, histologic analysis, and biomechanical tests were performed. RESULTS: Three months after implantation, micro-CT reconstruction showed that microstructural parameters of the BG group were significantly better compared with those in the other 2 groups (P<0.05). Histologic observation revealed that bone trabeculae around the screws in the BG group were more in number and denser than those in the control group. The average mineral apposition rate of the bone in the BG group was also higher than that in the other 2 groups (P<0.05). The mechanical properties in the BG group were also significantly higher than that in the control group. Six months after implantation, similar results except mineral apposition rate can be obtained among different groups. CONCLUSIONS: BG can significantly improve bone microstructure of the interface in osteoporosis condition and increase the hold strength of the pedicle screw.

Finite element study on the amount of injection cement during the pedicle screw augmentation.

STUDY DESIGN: A finite element analysis of the screw pullout procedure for the osteoporotic cancellous bone using screw-bone unit model without cortical layer. OBJECTIVE: The objective is to determine the region of effect (RoE) during the screw pullout procedure and predict the proper amount of injection cement (AIC) in screw augmentation. SUMMARY OF BACKGROUND DATA: For the osteoporotic spine, the AIC is a critical factor for the augmentation screw performance and leakage risk. There are few studies on the proper AIC in literature. METHODS: Three finite element models were established, 2 screw-foam models were used for validation study, and 1 screw-bone model was used for investigation of RoE and AIC. The simulations of screw pullout were conducted. A velocity loading of 0.01 mm/s with a maximum displacement of 2.7 mm was applied on the screw. For the validation, the screw-foam models with 2 different densities were used for comparison of pullout force with those published experimental data. After validation, the screw-bone model was used to investigate the RoE and predict the proper AIC during screw augmentation in spine surgery. RESULTS: In validation, the predicted pullout strengths were 2028.8 N for high-density foam model and 607 N for low-density foam model, respectively. They were in good agreement with those of the published experiment. In the screw-bone model, the simulations demonstrated that the RoE changed with the displacement of screw and reached the maximum when the displacement of screw was 1.8 mm. Similar trend was found for the AIC with the displacement. The proper AIC was 2.6 mL when the displacement of screw was 1.8 mm in this study. CONCLUSIONS: The RoE and proper AIC for augmentation were evaluated in the osteoporotic spine. This information could provide practical reference for screw augmentation in spinal decompression and instrumentation in the spine surgery.

Clinical assessment of a CMC/PEO gel to inhibit postoperative epidural adhesion formation after lumbar discectomy: a randomized, control study.

PURPOSE: To evaluate effectiveness of carboxymethylcellulose/polyethylene oxide (CMC/PEO) gel in improving clinical outcomes after the first-time lumbar discectomy. METHOD: Ninety-three patients with herniated lumbar disc at L4-L5 or L5-S1 were enrolled and randomized into two groups: CMC/PEO gel treatment group and control group. All the patients underwent laminotomy and discectomy by posterior approach. The preoperative and postoperative Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) scores for lower-back pain and leg pain were analyzed and compared between two groups at 30- and 60-day time points. RESULTS: No patient presented with any clinically measurable adverse event during surgery. There were no significant differences between the treated group and the control group on the preoperative ODI and VAS scores. In general, the ODI and VAS scores decreased in both groups at all the time points. At the 30-day time point, the VAS scores for back pain and leg pain and the ODI scores in treatment group were lower by 9.9 % (P = 0.0302), 27.0 % (P = 0.0002) and 16.3 % (P = 0.0007) than those in control group. And at the 60-day time point, the ODI and VAS scores further decreased in both groups. The VAS scores for leg pain in treatment group were lower by 4.5 % than that in the control group (P = 0.0149). However, no significant difference was detected between two groups on the ODI and VAS scores for back pain. CONCLUSIONS: The results demonstrated that CMC/PEO gel is effective in reducing posterior dural adhesions in the spine with no apparent safety issues. It can improve patients' postoperative clinical outcome.

The genetic background determines material-induced bone formation through the macrophage-osteoclast axis.

Osteoinductive materials are characterized by their ability to induce bone formation in ectopic sites. Thus, osteoinductive materials hold promising potential for repairing bone defects. However, the mechanism of material-induced bone formation remains unknown, which limits the design of highly potent osteoinductive materials. Here, we demonstrated a genetic background link among macrophage polarization, osteoclastogenesis and material-induced bone formation. The intramuscular implantation of an osteoinductive material in FVB/NCrl (FVB) mice resulted in more M2 macrophages at week 1, more osteoclasts at week 2 and increased bone formation after week 4 compared with the results obtained in C57BL/6JOlaHsd (C57) mice. Similarly, in vitro, with a greater potential to form M2 macrophages, monocytes derived from FVB mice formed more osteoclasts than those derived from C57 mice. A transcriptomic analysis identified Csf1, Cxcr4 and Tgfbr2 as the main genes controlling macrophage-osteoclast coupling, which were further confirmed by related inhibitors. With such coupling, macrophage polarization and osteoclast formation of monocytes in vitro successfully predicted in vivo bone formation in four other mouse strains. Considering material-induced bone formation as an example of acquired heterotopic bone formation, the current findings shed a light on precision medicine for both bone regeneration and the treatment of pathological heterotopic bone formation.

Hypoxia Drives Material-Induced Heterotopic Bone Formation by Enhancing Osteoclastogenesis via M2/Lipid-Loaded Macrophage Axis.

Heterotopic ossification (HO) is a double-edged sword. Pathological HO presents as an undesired clinical complication, whereas controlled heterotopic bone formation by synthetic osteoinductive materials shows promising therapeutic potentials for bone regeneration. However, the mechanism of material-induced heterotopic bone formation remains largely unknown. Early acquired HO being usually accompanied by severe tissue hypoxia prompts the hypothesis that hypoxia caused by the implantation coordinates serial cellular events and ultimately induces heterotopic bone formation in osteoinductive materials. The data presented herein shows a link between hypoxia, macrophage polarization to M2, osteoclastogenesis, and material-induced bone formation. Hypoxia inducible factor-1α (HIF-1α), a crucial mediator of cellular responses to hypoxia, is highly expressed in an osteoinductive calcium phosphate ceramic (CaP) during the early phase of implantation, while pharmacological inhibition of HIF-1α significantly inhibits M2 macrophage, subsequent osteoclast, and material-induced bone formation. Similarly, in vitro, hypoxia enhances M2 macrophage and osteoclast formation. Osteoclast-conditioned medium enhances osteogenic differentiation of mesenchymal stem cells, such enhancement disappears with the presence of HIF-1α inhibitor. Furthermore, metabolomics analysis reveals that hypoxia enhances osteoclastogenesis via the axis of M2/lipid-loaded macrophages. The current findings shed new light on the mechanism of HO and favor the design of more potent osteoinductive materials for bone regeneration.

Surgical treatment of osteoporotic thoracolumbar compressive fractures with open vertebral cement augmentation of expandable pedicle screw fixation: a biomechanical study and a 2-year follow-up of 20 patients.

BACKGROUND: The incidence of screw loosening increases significantly in elderly patients with severe osteoporosis. Open vertebral cement augmentation of expandable pedicle screw fixation may improve fixation strength in the osteoporotic vertebrae. MATERIALS AND METHODS: Twenty cadaveric vertebrae (L1-L5) were harvested from six osteoporotic lumbar spines. Axial pullout tests were performed to compare the maximum pullout strength (Fmax) of four methods: 1. Conventional pedicle screws (CPS), 2. Expandable pedicle screws (EPS), 3. Cement augmentation of CPS (cemented-CPS), 4. Cement augmentation of EPS (cemented-EPS). Thirty-six consecutive patients with single-vertebral osteoporotic compressive fractures received posterior decompression and spinal fusion with cemented-CPS (16 cases) or cemented-EPS (20 cases). Plain film and/or CT scan were conducted to evaluate the spinal fusion and fixation effectiveness. RESULTS: The Fmax and energy absorption of cemented-EPS were significantly greater than three control groups. The mean BMD in the severe osteoporosis group was significantly lower than that in the osteoporosis group (t = 2.04, P = 0.036). In the osteoporosis group, cemented-EPS improved the Fmax by 43% and 21% over CPS and cemented-CPS group. In the severe osteoporosis group, cemented-EPS increased the Fmax by 59%, 22%, and 26% over CPS, EPS, and cemented-CPS, respectively. The clinical results showed that all patients suffered from severe osteoporosis. Six months after operation, the JOA and VAS scores in cemented-EPS group improved from 11.4 ± 2.6 and 7.0 ± 1.4 mm to 24.9 ± 1.6 and 2.1 ± 1.3 mm, respectively. No screw loosening occurred in the cemented-EPS group and spinal fusion was achieved. In the cemented-CPS group, four screws loosened (4.2%) according to the radiolucency. Six months after operation, the JOA and VAS scores improved from 13.1 ± 1.9 and 7.6 ± 1.5 mm to 22.8 ± 2.2 and 2.5 ± 1.6 mm, respectively. No cement leaked into the spinal canal in both groups. CONCLUSIONS: Cemented-EPS could increase fixation strength biomechanically. It could reduce the risks of screw loosening in patients with severe osteoporosis, requiring instrumented arthrodesis.

BoLA-DRB3 gene polymorphism and FMD resistance or susceptibility in Wanbei cattle.

For the further characterization of foot-and-mouth disease virus (FMDV)-induced foot-and-mouth disease, we investigated the association between polymorphism of BoLA-DRB3 gene and FMD resistance/susceptibility of Wanbei cattle challenged with FMDV. One hundred cattle were challenged with FMDV and exon 2 of BoLA-DRB3 genes was amplified by hemi-nested polymerase chain reaction from asymptomatic animals and from animals with FMD. PCR products were characterized by the RFLP technique using restriction enzymes Hae III. The results revealed extensive polymorphisms, 6 RFLP patterns were identified. By analyzing alleles and genotypic frequencies between healthy and infection with FMD cattle, we found that allele Hae III A was associated with susceptibility to FMD in Wanbei cattle (P < 0.05), whereas Hae III C was associated with resistance to FMD (P < 0.01) and may have a strong protective effect against FMD. Hae IIICC and Hae III BC genotype were associated with resistance to FMD (P < 0.01). By contrast, Hae III AA genotype was associated with susceptibility to FMD (P < 0.01). Sequence analysis show that 89 amino acids were translated in exon 2 of BoLA-DRB3 and 13.70 % of nucleotide mutated, which resulted in 14.61 % of amino acid change. One PKC, one Tyr and one CAMP phosphorylation were increased; the hydrophobicity and secondary structure of proteins produced change after amino acid substitution. These results revealed that Wanbei cattle had the ability of resistance to disease by mutation which result changes of the protein structure to perform the regulation of the cell using different signaling pathways in the long process of choice evolution.

Oxidized Bletilla rhizome polysaccharide-based aerogel with synergistic antibiosis and hemostasis for wound healing.

Uncontrolled bleeding and infection following trauma remain a clinical challenge. Here, we developed a synergistic hemostatic and antibacterial aerogel dressing based on oxidized Bletilla rhizome polysaccharide Schiff Base (ORBPS) and polyvinyl alcohol (PVA) by using a combined freeze-drying/cross-linking process. Bletilla rhizome polysaccharide (RBP) was extracted by water extraction and alcohol precipitation. RBP contained mannose and glucose in the molar ratio of 2:1 and its molecular weight was 8.2 × 105 g/mol. ORBPS was prepared via Schiff base reaction between silver sulfadiazine and oxidized RBP (ORBP), and verified by FTIR and NMR spectra. The resultant ORBPS/PVA aerogel exhibited excellent antibacterial and hemostatic capabilities. The aerogel also showed good liquid absorption capacity and biocompatibility. Full-thickness skin defect experiments indicated the aerogel enhanced wound healing by reducing inflammation, promoting angiogenesis, and accelerating epithelialization. Therefore, ORBPS/PVA aerogel may be a potential hemostasis and anti-infection wound dressing.

Augmentation of pedicle screw stability with calcium sulfate cement in osteoporotic sheep: biomechanical and screw-bone interfacial evaluation.

STUDY DESIGN: Augmentation of pedicle screws with calcium sulfate cement (CSC) was performed in osteoporotic sheep. Biomechanical tests, micro-computed tomography (CT) analysis, and histological observation were performed. OBJECTIVE: To investigate the long-term biomechanical performance of pedicle screws augmented with CSC in vivo and evaluated the screw-bone interfacial bonding with micro-CT and histological techniques. SUMMARY OF BACKGROUND DATA: There is little information on the long-term biomechanical performance and screw-bone interfacial bonding of pedicle screws augmented with CSC in osteoporosis in vivo. METHODS: Twelve months after ovariectomy, bilateral pedicles of lumbar vertebrae (L1 to L5) of 6 female sheep were fixed with pedicle screws. One pedicle of each vertebral body was treated with a screw augmented with CSC (CSC group) and the contralateral pedicle was treated with a screw without any augmentation (control group). Three months later, the sheep were killed and biomechanical tests, micro-CT analysis, and histological observation were conducted on the isolated specimen vertebrae. RESULTS: Twelve months after ovariectomy, animal model of osteoporosis was established successfully. Both the axial and vertical stabilities of the pedicle screws in CSC group were significantly enhanced compared with those in the control group (P<0.05). Micro-CT reconstruction and analysis showed that there were more bone trabeculae around the screws in CSC group compared with those in control group (P<0.05), and the bone trabeculae were significantly denser than those in control group (P<0.05). Histological observation showed that CSC was completely degradated and bone trabeculae around the screws in CSC group were more and denser than that in the control group. Bone trabeculae held the screws tightly without any interspaces between screw and bone, which formed strong bonding between bone and screw. CONCLUSIONS: CSC can significantly improve screw-bone interfacial bonding and strengthen the long-term stability of pedicle screws in osteoporotic sheep. Augmentation with CSC may be a potentially useful method to increase the stability of pedicle screws in patients with osteoporosis.

A new method of partial screw augmentation in sheep vertebrae in vitro: biomechanical and interfacial evaluation.

STUDY DESIGN: Partial screw augmentation was carried out by the injection of polymethylmethacrylate (PMMA) through the novel tap into the bone tissue in sheep vertebrae in vitro. Biomechanical tests and microcomputerized tomography analysis were done. OBJECTIVE: To evaluate the stability of the screw and the interface between the bone and the screw in partial screw augmentation. SUMMARY OF BACKGROUND DATA: Augmentation of the pedicle screw with PMMA improves screw stability significantly. However, it results in the full envelopment of the screw by PMMA and the formation of a full "screw-PMMA-bone" interface, which may increase the difficulties in screw removal. Therefore, it is urgent to develop a novel method to augment screw fixation, which avoids full wrapping of PMMA around the screw and facilitates screw removal. We designed a novel tap with an inner hollow and the multiple lateral apertures. METHODS: A total of 78 fresh adult sheep lumbar vertebrae were randomly divided into 3 groups. No screw augmentation was performed in the control group. The pilot hole was filled with PMMA in the full screw augmentation group, whereas PMMA was injected through the tap into the bone tissue in the partial screw augmentation group. Pedicle screws were ultimately inserted into all the holes. Axial pullout tests, cyclic bending tests, and microcomputerized tomography analysis were carried out 24 hours after screw fixation. RESULTS: Both partial screw augmentation and full screw augmentation caused significant increase in pedicle screw stability compared with the control group in both the axial pullout tests and the cyclic bending resistance tests. Partial screw augmentation resulted in the formation of a partial "screw-bone" interface and a partial screw-PMMA-bone interface, which seems like 3 anchors or roots extending and fixing in the bone tissue in a cross section of the interface. It was obviously different from the complete screw-PMMA-bone interface with a complete PMMA mantle around the screw in the full screw augmentation group. CONCLUSIONS: Our proof-of-concept study showed that partial screw augmentation could enhance pedicle screw fixation strength, avoided the full surrounding of the PMMA around the screw, and generated a partial screw-PMMA-bone and a partial screw-bone interface. Partial screw augmentation may be a potential method to augment pedicle screw stability.

Biomechanical comparison of different techniques in primary spinal surgery in osteoporotic cadaveric lumbar vertebrae: expansive pedicle screw versus polymethylmethacrylate-augmented pedicle screw.

INTRODUCTION: Transpedicular fixation can be challenging in the osteoporotic spine. Expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) were both used to increase screw stability. However, there are a little or no biomechanical comparisons of EPS and PMMA-PS, especially in primary spinal surgery in osteoporotic vertebrae. The purpose of this study was to compare the stability of EPS and PMMA-PS in primary spinal surgery. MATERIALS AND METHODS: Fifteen osteoporotic vertebrae were randomly divided into three groups. The conventional pedicle screw (CPS) was inserted in CPS group, the pilot hole was filled with PMMA followed by CPS insertion in PMMA-PS group, and EPS was inserted in EPS group. Twenty-four hours later, X-ray and CT examination and biomechanical tests were performed to all vertebrae. RESULTS: In PMMA-PS group, PMMA existed in bone tissue around the CPS in both vertebral body and pedicle of vertebral arch, and PMMA surrounding the screw formed a spindle-shaped structure in vertebral body. In EPS group, anterior part of EPS presented an obvious expansion in vertebral body and formed a clawlike structure. Screw stabilities in PMMA-PS and EPS groups were significantly enhanced compared with those in CPS group (P < 0.05). However, there was no significant difference between PMMA-PS and EPS groups (P > 0.05). CONCLUSION: Expansive pedicle screw can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in primary surgery in osteoporotic vertebrae. In addition, EPS can overcome pedicle fracture, leakage and compression caused by lager screw and augmentation with PMMA. We propose that EPS is an effective, safe and easy method and has a great application potential in augmentation of screw stability in osteoporosis in clinic.

Association Between the TaqI (rs731236 T>C) Gene Polymorphism and Dental Caries Risk: A Meta-analysis.

Objective: This study investigated the association of the TaqI (rs731236 T>C) polymorphism in the VDR gene with dental caries. Methods: A comprehensive literature search was performed in PubMed, Web of Science, Embase, SinoMed (the Chinese biomedical literature service system), and the Wiley Online Library. Overall comparisons and subgroup analyses based on ethnicity and the presence of dental caries in dentition were performed. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess associations between gene polymorphisms and the risk of dental caries. Results: Seven articles were included in this meta-analysis. The pooled results revealed a significant association of the TaqI (rs731236 T>C) polymorphism with dental caries in the allele contrast model (C vs. T: OR = 1.24, 95% CI = 1.07-1.44, I2 = 42%, p = 0.005) and in the recessive genetic model (CC vs. TT/CT: OR = 1.38, 95% CI = 1.03-1.84, I2 = 0%, p = 0.03). A stratified analysis based on ethnicity revealed a significant association between the TaqI (rs731236 T>C) polymorphism and the risk of dental caries in Asians (C vs. T: OR = 1.28, 95% CI = 1.06-1.54, I2 = 60%, p = 0.009). Subgroup analysis based on the presence of dental caries in dentition found a significant association of the TaqI (rs731236 T>C) polymorphism with permanent tooth caries in the allele contrast model (C vs. T: OR = 1.40, 95% CI = 1.11-1.77, I2 = 76%, p = 0.005) and the recessive genetic model (CC vs. TT/CT: OR = 1.44, 95% CI = 1.03-2.00, I2 = 0%, p = 0.03). Conclusion: The results of this meta-analysis suggest that the C allele and CC genotype of the TaqI (rs731236 T>C) polymorphism in the VDR gene are associated with an increased risk of dental caries.

Polydopamine-carbon dots functionalized hollow carbon nanoplatform for fluorescence-imaging and photothermal-enhanced thermochemotherapy.

The low power photothermal therapy can reduce the tissue damage caused by laser irradiation, thus the near-infrared (NIR) absorbing vehicles with high photothermal conversion efficiency are demanded in the low power treatment. Herein, the NIR-absorbing agent polydopamine (PDA) and carbon dots (CDs) were gated on the openings of hollow mesoporous carbon (HMC) to construct a photothermal enhanced multi-functional system (HMC-SS-PDA@CDs). Interestingly, the fluorescence emission wavelength of HMC-SS-PDA@CDs was red-shifted by FRET effect between PDA and CDs, which solved the dilemma of fluorescence quenching of carbon-based materials and was more conducive to cell imaging. The modification of PDA@CDs not only acts as the gatekeepers to realize multi-responsive release of pH, GSH and NIR, but also endows the HMC vehicle with excellent photothermal generation capacity, the possibility for bio-imaging as well as the enhanced stability. Naturally, both the cytological level and the multicellular tumor sphere level demonstrate that the delivery system has good low-power synergistic therapeutic with combination index (CI) of 0.348 and imaging effects. Meanwhile, the combined treatment group showed the highest tumor inhibition rate of 92.6% at 0.75 W/cm2. Therefore, DOX/HMC-SS-PDA@CDs nano-platform had broad application prospects in low power therapy and convenient imaging of carbon-based materials.

In Situ Regulation of Macrophage Polarization to Enhance Osseointegration Under Diabetic Conditions Using Injectable Silk/Sitagliptin Gel Scaffolds.

As a chronic inflammatory disease, diabetes mellitus creates a proinflammatory microenvironment around implants, resulting in a high rate of implant loosening or failure in osteological therapies. In this study, macroporous silk gel scaffolds are injected at the bone-implant interface for in situ release of sitagliptin that can regulate macrophage response to create a prohealing microenvironment in diabetes mellitus disease. Notably, it is discovered that sitagliptin induces macrophage polarization to the M2 phenotype and alleviates the impaired behaviors of osteoblasts on titanium (Ti) implants under diabetic conditions in a dose-dependent manner. The silk gel scaffolds loaded with sitagliptin elicite a stronger recruitment of M2 macrophages to the sites of Ti implants and a significant promotion of osteointegration, as compared to oral sitagliptin administration. The results suggest that injectable silk/sitagliptin gel scaffolds can be utilized to modulate the immune responses at the bone-implant interface, thus enhancing bone regeneration required for successful implantation of orthopedic and dental devices in diabetic patients.